1. Field of Invention
The invention relates to a correction apparatus and correction method for sewing data to be used on a sewing machine that moves a needle bar upward and downward and a frame holding an object to be sewn in the X- and Y-axis directions to form a pattern on the object to be sewn.
2. Description of Related Art
There is a sewing machine that can form patterns on various kinds of objects to be sewn. For example, a sewing system for embroidering is designed to sew an embroidery pattern on a hat as an object to be sewn by moving a needle bar having a needle up and down and moving an attachment frame to which the hat is attached. The sewing system for embroidery comprises the attachment frame movable in the X- and Y-axis directions that cross each other, an actuator that drives the attachment frame, a needle bar movable upward and downward together with a needle, an actuator that drives the needle bar, and a controller that drives and controls each actuator. With regards to the attachment frame that holds a hat or cap, there are two types: one has two fixing portions that holds a hat both at a visor side and at a crown side; and the other has a single fixing portion that hold a hat only at a visor side. The controller, for example, drives and controls each actuator based on the sewing data read into an internal memory from an outside recording medium, to move the needle up and down and the attachment frame in the X and Y directions with the needle movement. To secure the movement amount in the X or Y direction, there is a structure in which the attachment frame is rotatable. Thus, as shown in FIG. 9, a specified embroidery pattern 72 is to be embroidered on a specified portion, e.g. the front, of a cap 71 attached to the attachment frame.
The controller processes the sewing data in accordance with a specified control program previously stored into the internal memory.
However, in the above-mentioned sewing system, the cap 71 is the main object to be sewn. The cap 71 has a substantially conical shape, and a diameter toward a crown side 71a is smaller than that toward a visor side 71b. Therefore, when the attachment frame is moved to move the cap 71, the movement amount toward the crown 71a tends to become smaller than that toward the visor 71b. In particular, the arrangement in which the attachment frame is rotated in conformity to the shape of the cap 71 is more likely to show this tendency. Therefore, when an embroidery pattern 72 is embroidered on the cap 71, the actual width of the pattern 72 becomes narrower in the direction from the visor side toward the crown side as shown in FIG. 10 (b), in contrast to an expected pattern as shown in FIG. 10 (a).
On the other hand, in the sewing system using the attachment frame that has only one fixing portion at the visor side 71b for fixing the cap 71, when the cap 71 is moved along with the attachment frame, there is a possibility that the movement toward the crown side 71a becomes smaller than that toward the visor side 71b. This case also includes the above problem that the actual width of the sewn pattern is not equal at the visor side 71b and the crown side 71a.